He specifically cited bad battery life on the ROG Ally and Lenovo Go, saying that getting only one hour of battery life isn't enough. The Steam Deck (especially the OLED model) does a lot better battery wise, but improving power efficiency should really help with any games that are maxing out the Deck's power.
The big thing that actually defines FSR2 is that it has access to a bunch more data, particularly the depth buffer, motion vectors, and also, as you said, uses data from previous frames.
The camera jiggle is mostly just to avoid shimmering when the camera is stationary.